The present invention relates to the field of mass storage devices. More particularly, this invention relates to a disk drive which includes a slider having a roughened air-bearing surface.
One of the key components of any computer system is a place to store data. One common place for storing data in a computer system is on a disk drive. The most basic parts of a disk drive are a disk that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disk drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disk surface. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk. The magnetic transducer translates electrical signals into magnetic field signals that actually record the data xe2x80x9cbits.xe2x80x9d
The transducer is typically housed within a small ceramic block called a slider. The slider is passed over the rotating disk in close proximity to the disk. The transducer can be used to read information representing data from the disk or write information representing data to the disk. When the disk is operating, the disk is usually spinning at relatively high revolutions per minute (xe2x80x9cRPMxe2x80x9d). A current common rotational speed is 7200 RPM. Rotational speeds in high-performance disk drives are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future.
The slider is usually aerodynamically designed so that it flies on the cushion of air that is dragged by the disk. The slider has an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. The air-bearing surface is that surface of the slider nearest the disk as the disk drive is operating. Air is dragged between the rails and the disk surface causing an increase in pressure which tends to force the head away from the disk. Simultaneously, air rushing past the depression in the air-bearing surface produces a lower than ambient pressure area at the depression. This vacuum effect counteracts the pressure produced at the rails. The opposing forces equilibrate so the slider flies over the surface of the disk at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disk surface and the transducing head. This film minimizes the friction and resulting wear that would occur if the transducing head and disk were in mechanical contact during disk rotation.
The best performance of the disk drive results when the slider is flown as closely to the surface of the disk as possible. In operation, the distance between the slider and the disk is very small; currently xe2x80x9cflyxe2x80x9d heights are about 1-2 micro inches.
Information representative of data is stored on the surface of the memory disk. Disk drive systems read and write information stored on tracks on memory disks. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disk, read and write information on the memory disks when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disk. The transducer is also said to be moved to a target track. As the memory disk spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disk. Similarly, reading data on a memory disk is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disk drives, the tracks are a multiplicity of concentric circular tracks. In other disk drives, a continuous spiral is one track on one side of a disk drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held accurately during a read or write operation using the servo information.
One of the most critical times during the operation of a disk drive occurs just before the disk drive shuts down or during the initial moment when the disk drive starts. When shutdown occurs, the slider is typically flying over the disk at a very low height. Just before shutdown, the slider is moved to a non-data containing area of the disk where it is landed. During landing, the slider skids to a stop. When the disk drive starts, the slider skids across the non-data containing portion of the disk until the velocity of the slider is sufficient to produce lift between the slider and the disk.
In the past, the surface of the disk was textured to keep contact points between the disk and the slider to a minimum. Currently, it has been found that disks with smooth surfaces have better magnetic characteristics. The recording density of the disk is highest when the spacing between the transducing head and the magnetic layer is minimized. By reducing the roughness or texturing on the disk, the spacing between the transducing head and the magnetic layer on the disk can also be reduced. When smooth sliders are landed on disks formed with a smooth surface, problems occur. One of the larger problems is that a stiction force occurs between the slider and the disk surface. Stiction is static friction and is proportional to the size of a meniscus formed by the lubricant on the disk. When a smooth slider lands on a smooth disk, the stiction forces are high. In some instances, the stiction forces may cause the slider to separate from the suspension. In other words, the stiction forces are so high that the slider rips from the suspension to which it is mounted.
One solution includes reducing the contact area of the air-bearing surface. However, even when this is done, frictional forces due to stiction remain and affect the performance of the air-bearing surface and slider. Evidence of air-bearing instability has been observed.
Thus, there is a need for a method and apparatus for reducing the stiction forces produced between the surface of the disk and the slider. There is also a need for a method and apparatus that allows for use of a smooth disk so that the spacing between the transducing head associated with the slider and the disk can be controlled and kept to a minimum to provide for an enhanced recording density of the information stored on the disk. There is also a need for a method and apparatus that provides for reduced stiction forces and yet still provides a stable air-bearing surface and slider. The method must also produce an air-bearing that is rugged and durable enough to last for the life of the disk drive. The method and apparatus must also be made of materials with minimal outgassing so that contaminants will not be added to the disk drive enclosure which could contaminant the lubricant on the disk.
An information handling system, such as a disk drive, includes a base, a disk stack rotatably attached to the base, and an actuator assembly movably attached to the base. The actuator assembly also includes a load spring and a slider attached to said load spring. The slider and load spring are attached to form a gimballing connection between the slider and the load spring. The slider includes an air-bearing surface which has a contact area. The slider also includes a transducer. The transducer is typically located near said contact area. The contact area includes a roughened surface portion and a smooth surface portion. The smooth surface portion is adjacent the transducer. The roughened surface portion is rougher than the smooth surface portion. The roughened surface portion is also rougher than the other surfaces associated with the air-bearing surface of the slider.
The roughened surface portion of the contact area is formed in one of several ways. If the slider is comprised of a multi-phase material, a selective etchant can be applied to the contact area for a selected amount of time. The selective etchant will act to remove a portion of at least one of the phases of the material and will be less active or inactive in removing at least another of the phases of the material. The amount of material removed using the selective etchant will be determined by the concentration of the etchant as well as the amount of time the etchant is left on the surface of the multi-phase material. The grain size of the materials used in the multi-phase material can also be used to determine the surface roughness of the contact portion. If the body of the slider is made of a single-phase material, this technique requires removal of a portion of the contact area of the air-bearing bearing surface. The next step includes depositing an etchable multi-phase material on the portion of the contact area. The selective etchant is then applied to the multi-phase phase material at the contact area. At least one of the phases is removed by the selective etchant to form a roughened surface. The selective etchant is typically a wet or chemical etchant that reacts with one of the phases of the multi-phase material.
The other process is a dry process that can be used on any material. Photoresist is applied to the contact area. The photoresist is exposed and developed in certain areas to form a defined pattern across the contact area. Dry etch removal techniques are then used to remove material of the slider such that the defined pattern is transferred onto the slider. The photolithography technique using a dry etch works on both single-phase and multi-phase materials.
Advantageously, a roughened portion of the contact surface reduces the stiction forces produced between the surface of the disk and the slider and allows landing of a slider onto a smooth disk. Furthermore, since a smooth disk can be used the spacing between the transducing head associated with the slider and the disk can be controlled and minimized to provide for an enhanced recording density of the information stored on the disk. The roughened contact area of the air-bearing surface not only reduces stiction forces between the disk and the slider, but also provides a stable air-bearing surface for the slider. The resulting air-bearing is rugged and durable. The materials used to form the roughened surface are removed so the only materials remaining are those already in the drive. Thus, outgassing problems are minimal.